To gain that fourth seed, he beat Novak Djokovic to win the Italian Open, then took out Roger Federer to win in Montreal two weeks ago. He is some experts’ intriguing choice to post his first Grand Slam title here.

ESPN partner Brad Gilbert said if Federer doesn’t triumph here, “Zverev is my second favorite to win the tournament.’’

None of it has flustered the cocky surfer boy Zverev, whose older brother Mischa is a top-30 player.

Alexander Zverev celebrates after winning the Citi Open.AP

“You probably expect me to be super surpised,’’ Zverev said Saturday of his emergence. “Obviously I wouldn’t have expected it but what work I have done in the offseason, and throughout the season, my whole team was working towards something like this.

“I’m super happy the way things are going but I’m not going to be satisfied with just being [the] No. 3 seed. It doesn’t matter at the end of the tournament what seed you were. It only matters how far you went.’’

His only disconcerting dip came in an early-round defeat in the final tune-up in suburban Cincinnati 11 days ago to young American Frances Tiafoe, but he made the most of his extra time. He got to New York early — actually heading over last week to the Hamptons, where his friend has a place by the ocean.

“I actually went to the beach a lot, played a bit of golf, just relaxed a lot, didn’t do physical activities,’’ Zverev said. “Then Monday started full practice again.’’

Winning two ATP Masters events — the first non-Big 4 player to do so since 2007 — plus a title at the smaller Open tune-up in Washington last month has his stock soaring. The Open’s decimated men’s field also gives him a big opportunity, especially if Federer’s back flares up.

Last year’s Open finalists, Stan Wawrinka and Novak Djokovic, are out and No. 2 seed Andy Murray withdrew Saturday. Zverev was on Murray’s half of the draw and away from the…